Corresponding by telegram about politician involved in row (10)
I believe the answer is:
comparable
'corresponding' is the definition.
(synonyms)
'telegram about politician involved in row' is the wordplay.
'telegram' becomes 'cable' (cable is a kind of telegram).
'about' means one lot of letters goes inside another.
'politician' becomes 'mp' (Member of Parliament).
'involved in' indicates putting letters inside.
'row' becomes 'oar' (oar can mean to row with oars).
'mp' placed into 'oar' is 'ompar'.
'cable' going around 'ompar' is 'COMPARABLE'.
'by' is the link.
(Another definition for comparable that I've seen is " Similar".)